From: Jonathan Nieder <jrnieder@gmail.com>
To: git@vger.kernel.org
Cc: David Barr <david.barr@cordelta.com>,
Thomas Rast <trast@student.ethz.ch>,
Ramkumar Ramachandra <artagnon@gmail.com>
Subject: [PATCH 12/12] vcs-svn: teach line_buffer about temporary files
Date: Sun, 2 Jan 2011 21:10:59 -0600 [thread overview]
Message-ID: <20110103031059.GE10143@burratino> (raw)
In-Reply-To: <20110103030328.GA10143@burratino>
It can sometimes be useful to write information temporarily to file,
to read back later. These functions allow a program to use the
line_buffer facilities when doing so.
It works like this:
1. find a unique filename with buffer_tmpfile_init.
2. rewind with buffer_tmpfile_rewind. This returns a stdio
handle for writing.
3. when finished writing, declare so with
buffer_tmpfile_prepare_to_read. The return value indicates
how many bytes were written.
4. read whatever portion of the file is needed.
5. if finished, remove the temporary file with buffer_deinit.
otherwise, go back to step 2,
The svn support would use this to buffer the postimage from delta
application until the length is known and fast-import can receive
the resulting blob.
Based-on-patch-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
David, this is another piece of infrastructure from early svn-fe3
history. I've cleaned up the API a little bit but the idea is the
same. Thank you.
vcs-svn/line_buffer.c | 24 ++++++++++++++++++++++++
vcs-svn/line_buffer.h | 7 ++++++-
vcs-svn/line_buffer.txt | 22 ++++++++++++++++++++++
3 files changed, 52 insertions(+), 1 deletions(-)
diff --git a/vcs-svn/line_buffer.c b/vcs-svn/line_buffer.c
index e29a81a..aedf105 100644
--- a/vcs-svn/line_buffer.c
+++ b/vcs-svn/line_buffer.c
@@ -25,6 +25,14 @@ int buffer_fdinit(struct line_buffer *buf, int fd)
return 0;
}
+int buffer_tmpfile_init(struct line_buffer *buf)
+{
+ buf->infile = tmpfile();
+ if (!buf->infile)
+ return -1;
+ return 0;
+}
+
int buffer_deinit(struct line_buffer *buf)
{
int err;
@@ -35,6 +43,22 @@ int buffer_deinit(struct line_buffer *buf)
return err;
}
+FILE *buffer_tmpfile_rewind(struct line_buffer *buf)
+{
+ rewind(buf->infile);
+ return buf->infile;
+}
+
+long buffer_tmpfile_prepare_to_read(struct line_buffer *buf)
+{
+ long pos = ftell(buf->infile);
+ if (pos < 0)
+ return error("ftell error: %s", strerror(errno));
+ if (fseek(buf->infile, 0, SEEK_SET))
+ return error("seek error: %s", strerror(errno));
+ return pos;
+}
+
int buffer_read_char(struct line_buffer *buf)
{
return fgetc(buf->infile);
diff --git a/vcs-svn/line_buffer.h b/vcs-svn/line_buffer.h
index 630d83c..96ce966 100644
--- a/vcs-svn/line_buffer.h
+++ b/vcs-svn/line_buffer.h
@@ -15,12 +15,17 @@ struct line_buffer {
int buffer_init(struct line_buffer *buf, const char *filename);
int buffer_fdinit(struct line_buffer *buf, int fd);
int buffer_deinit(struct line_buffer *buf);
+void buffer_reset(struct line_buffer *buf);
+
+int buffer_tmpfile_init(struct line_buffer *buf);
+FILE *buffer_tmpfile_rewind(struct line_buffer *buf); /* prepare to write. */
+long buffer_tmpfile_prepare_to_read(struct line_buffer *buf);
+
char *buffer_read_line(struct line_buffer *buf);
char *buffer_read_string(struct line_buffer *buf, uint32_t len);
int buffer_read_char(struct line_buffer *buf);
void buffer_read_binary(struct line_buffer *buf, struct strbuf *sb, uint32_t len);
void buffer_copy_bytes(struct line_buffer *buf, uint32_t len);
void buffer_skip_bytes(struct line_buffer *buf, uint32_t len);
-void buffer_reset(struct line_buffer *buf);
#endif
diff --git a/vcs-svn/line_buffer.txt b/vcs-svn/line_buffer.txt
index 4e8fb71..e89cc41 100644
--- a/vcs-svn/line_buffer.txt
+++ b/vcs-svn/line_buffer.txt
@@ -24,6 +24,28 @@ The calling program:
When finished, the caller can use `buffer_reset` to deallocate
resources.
+Using temporary files
+---------------------
+
+Temporary files provide a place to store data that should not outlive
+the calling program. A program
+
+ - initializes a `struct line_buffer` to LINE_BUFFER_INIT
+ - requests a temporary file with `buffer_tmpfile_init`
+ - acquires an output handle by calling `buffer_tmpfile_rewind`
+ - uses standard I/O functions like `fprintf` and `fwrite` to fill
+ the temporary file
+ - declares writing is over with `buffer_tmpfile_prepare_to_read`
+ - can re-read what was written with `buffer_read_line`,
+ `buffer_read_string`, and so on
+ - can reuse the temporary file by calling `buffer_tmpfile_rewind`
+ again
+ - removes the temporary file with `buffer_deinit`, perhaps to
+ reuse the line_buffer for some other file.
+
+When finished, the calling program can use `buffer_reset` to deallocate
+resources.
+
Functions
---------
--
1.7.4.rc0.580.g89dc.dirty
next prev parent reply other threads:[~2011-01-03 3:11 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-24 8:05 [PATCH 0/4] teach vcs-svn/line_buffer to handle multiple input files Jonathan Nieder
2010-12-24 8:08 ` [PATCH 1/4] vcs-svn: eliminate global byte_buffer Jonathan Nieder
2010-12-24 8:17 ` [PATCH 2/4] vcs-svn: replace buffer_read_string memory pool with a strbuf Jonathan Nieder
2010-12-24 8:18 ` [PATCH 3/4] vcs-svn: collect line_buffer data in a struct Jonathan Nieder
2010-12-24 8:28 ` [PATCH 4/4] vcs-svn: teach line_buffer to handle multiple input files Jonathan Nieder
2011-01-03 0:49 ` [PATCH 0/4] teach vcs-svn/line_buffer " Jonathan Nieder
2011-01-03 0:50 ` [PATCH 5/8] vcs-svn: make test-line-buffer input format more flexible Jonathan Nieder
2011-01-03 0:51 ` [PATCH 6/8] tests: give vcs-svn/line_buffer its own test script Jonathan Nieder
2011-01-03 0:52 ` [PATCH 7/8] vcs-svn: tweak test-line-buffer to not assume line-oriented input Jonathan Nieder
2011-01-03 1:07 ` [PATCH 8/8] t0081 (line-buffer): add buffering tests Jonathan Nieder
2011-01-03 1:34 ` Jonathan Nieder
2011-01-03 3:03 ` [PATCHES 9-12/12] line_buffer: more wrappers around stdio functions Jonathan Nieder
2011-01-03 3:05 ` [PATCH 09/12] vcs-svn: add binary-safe read function Jonathan Nieder
2011-01-03 3:06 ` [PATCH 10/12] vcs-svn: allow character-oriented input Jonathan Nieder
2011-01-03 3:09 ` [PATCH 11/12] vcs-svn: allow input from file descriptor Jonathan Nieder
2011-01-03 3:10 ` Jonathan Nieder [this message]
2011-01-22 6:42 ` [FYI/PATCH] vcs-svn: give control over temporary file names Jonathan Nieder
2011-02-26 11:44 ` [PULL svn-fe] fast-import 'ls', line-buffer changes Jonathan Nieder
2011-02-26 12:03 ` David Michael Barr
2011-02-28 6:15 ` Junio C Hamano
2011-02-28 21:32 ` [PATCH svn-fe] fast-import: make code "-Wpointer-arith" clean Jonathan Nieder
2011-02-28 21:36 ` Sverre Rabbelier
2011-02-28 22:05 ` Junio C Hamano
2011-02-28 23:15 ` Jonathan Nieder
2011-03-01 0:41 ` Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110103031059.GE10143@burratino \
--to=jrnieder@gmail.com \
--cc=artagnon@gmail.com \
--cc=david.barr@cordelta.com \
--cc=git@vger.kernel.org \
--cc=trast@student.ethz.ch \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).